1. Field of the Invention
The present invention relates to railroad trains formed of intermodal over-the-highway trailers coupled together. More particularly, this invention relates to a novel, low-cost ramp system for raising and lowering intermodal highway trailers to facilitate assembly with or disassembly from railtrucks for intermodal transportation, which system may be portable and is not necessarily limited to highway trailers having a particular wheel suspension system.
2. Description of the Prior Art
A variety of types of intermodal transportation have been developed which utilize a train of highway trailers to travel along railroad track. Such systems attempt to utilize the flexibility and efficiency of highway trailers or semi-trailers for short hauling of units and yet achieve the fuel, labor and equipment cost advantages of railroads for long hauls.
For many decades, the railroad industry has attempted to create an intermodal alternative to the truck which could harness these economies by piggy-backing one mode on top of the other. The typical system of placing highway trailers on railroad flatcars, however, has cost penalties much greater than the economies of truck transportation alone. These disadvantages have led to the development of alternative intermodal systems.
One intermodal system which was developed to attempt to combine the capabilities of rail and highway in one vehicle is set forth in U.S. Pat. No. 4,202,277 to Browne et al. This system includes a highway trailer that may be operated over the highway as a truck trailer and over the railroad in unit trains. The trailer body has both highway and rail running gear, both supported by an air suspension system, and is independently supported upon the highway running gear for highway operation, and upon the railroad railtruck bogies for railroad operation. The air spring suspension allows the independent raising and lowering of the highway running gear and the railroad bogie for selective use in the railroad mode or the highway mode. The semi-trailers are couplable end-to-end to form a train of multiple semi-trailers in the railroad mode of travel.
Another approach to intermodal systems is set forth in U.S. Pat. No. 4,669,391 to Wicks et al., which is incorporated herein by reference. This system includes a highway trailer which is mounted on a conventional railtruck with an intermodal adapter. In order to couple the trailer to the railtruck, the trailer is backed up to the railtruck bogie and the air suspension is inflated to lift the trailer body a few inches. Further backing of the trailer allows mounting onto the bogie. Once mounted, lock pins secure the trailer body and coupling saddle into a unitized rail platform. The air suspension air bags are then deflated and coil springs lift the highway trailer tires to clear the rail.
While both of the above systems are commercially successful systems, both require the utilization of air spring suspension systems. The commercial embodiment of the Browne et al. system utilizes the air spring suspension system to raise and lower the highway running gear and the railroad bogie. The commercial embodiment of the Wicks et al. system utilizes the air spring suspension system, or an alternate hydraulic system, to raise the trailer the appropriate distance to allow mounting onto the bogie.
As a result of the high cost and limited availability of intermodal highway trailers with air spring suspension systems, there is a need for a trailer-bogie mounting system which is able to accommodate both air spring and standard spring suspension intermodal trailers and yet utilize the available commercial railtruck units. Such a mounting system would allow utilization of intermodal systems without the need for a costly air spring suspension system.
Other prior art systems, such as the one shown in U.S. Pat. No. 2,963,986 to Dobson, which have attempted to depress the track in order to raise the level of the trailer with respect to the rail bogie, fail to provide the necessary portability for versatility and to allow other uses of the railtrack when not used to assemble intermodal systems. These prior art systems are also not usable with certain commercially-available intermodal system trailers and railtrucks.
Accordingly, a need exists for a system for connection of intermodal highway trailers to, and disconnection of intermodal highway trailers from, railtrucks for intermodal transportation, which system may be portable and not limited to a particular type of trailer suspension system, but may in fact be utilized with conventional, lower cost spring suspension intermodal trailers and existing intermodal railtrucks.